|[[Image:Conventional_gravity_sewer.png |right|300px]]
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[[Image:Icon_conventional_gravity_sewer.png |right|95px]]
'''Conventional Gravity Sewers are large networks of underground pipes that convey blackwater, greywater and stormwater from individual households to a centralized treatment facility using gravity (and pumps where necessary).'''
Manholes are installed wherever there is a change of grade or alignment and are used for inspection and cleaning. Sewers can be dangerous and should only be maintained by professionals although, in well-organised communities, the maintenance of tertiary networks might be handed over to a well-trained group of community members.
==Acknowledgements=={{:Acknowledgements Sanitation}} ==References and external links==
* ASCE (1992). Gravity Sanitary Sewer Design and Construction, ASCE Manuals and Reports on Engineering Practice No. 60, WPCF MOP No. FD-5. American Society of Civil Engineers, New York. (A standard design text used in North America although local codes and standards should be assessed before choosing a design manual.)
* Tchobanoglous, G., Burton, FL. and Stensel, HD. (2003). Wastewater Engineering: Treatment and Reuse, 4th Edition. Metcalf & Eddy, New York.
==Acknowledgements==
{{:Acknowledgements Sanitation}}
